Hollongapar Gibbon Wildlife sanctuary, more popularly known as Gibbon Wildlife Sanctuary named after Hoolock Gibbon covers an area of 20.98 square kilometers (including the area under Military Engineering Services of Indian Army) at Jorhat district of Assam. The Hoollongapar Gibbon Wildlife Sanctuary was earlier known as Hoollongapar Forest during British period in 1881. This sanctuary is approximately 19 km from Jorhat's town centre and 5 km from Mariani.

The Hoollongapar Gibbon Sanctuary contains India's only gibbons - the hoolock gibbons, and Northeastern India's only nocturnal primate - the Bengal slow loris. The upper canopy of the forest is dominated by the Hollong tree (Dipterocarpus macrocarpus), while the Nahar (Mesua ferrea) dominates the middle canopy. The lower canopy consists of evergreen shrubs and herbs. The habitat is threatened by illegal logging, encroachment of human settlements, and habitat fragmentation.

The sanctuary officially extends to the Dissoi Valley Reserve Forest, Dissoi Reserve Forest, and Tiru Hill Reserve Forest, which are used as dispersal areas for Indian elephants (Elephas maximus indicus) and other animals. Three extensive tea gardens that belong to the estates of Dissoi, Kothalguri, and Hoolonguri span the distance between the Hoollongapar Gibbon Sanctuary and the nearest forests in Nagaland, the Dissoi Valley Reserve Forest. The tea gardens include Katonibari, Murmurai, Chenijan, Koliapani, Meleng, Kakojan, Dihavelleoguri, Dihingapar, Kothalguri, Dissoi and Hoolonguri. Neighboring villages include Madhupur, Lakhipur, Rampur, Fesual A (the western part), Fesual B (the eastern part), Katonibari, Pukhurai, Velleoguri, Afolamukh, and Kaliagaon.